Method of making electric coils



Nov. 16, 1943. T. A. RICH METHOD OF MAKING ELECTRIC COILS Filed May 19, 1942 h ...m PR WM er fl vmf m w e T w H b H is Attprh e stationary coils l9 and 20.

Patented Nov. 16, 1943 g mm s 'r s assess;

mnrnon mammal: cons Theodore A. Rich, Schenectady, N. Y., asslgnor to General Electric Comp r New York any, a corporation of ApplicationMay 19, 1942, Serial No. 443,672 I 4 Claims. 01'. 29-1555) F My invention relates a method of making electrically insulated coils particularly flat spirally wound coils suitable for use .in certain electrical measuring instruments. f

The object of my invention is to provide coils of-the character described; at low expense and -coils which .are well insulated, self-supporting and free from objectionable metallic parts here- The features oi my;;inventicn--which are'believed to benovel andpatentable will be pointed out in the claims appended hereto. For a'better understanding of my invention reference is rnade .in the following description to the accompanying @drawing in which Fig. 1 represents an exploded perspective view of anelectrlcalmeasuring instrument-having coils made in accordancelwith my invention; Figs. 2 and 3 represent initial-steps employed in the method of winding of the coil on a-metal .form,rFig. 4 represents the step of replacing .the metal form with insulation, Fig. 5'

represents a; mold and showshow two coils may a be secured in fixed relation by a folded insulating compound supporting structure, and Fig. 6 shows a coil assembly as it comes from the mold preparatory to sawing it into a plurality of flat coil sections of the character shown in Fig. 1.

In Fig. l l I .have represented an electrical measuring instrument'having a rotating element comprising the shaft 10, moving coil I l, pointer 12, damping vane I3 and balancing arms N. Current may be conducted to the coil II by spirals l5 and which may also furnish the retot-ore employed in the formation-oi suchcoils.

. that of the moving coil and hence,,-a-repulslon Fig. 1 shows the stationary and moving coils separated vertically a much. greater distance than would be the casein an actual. instrument since ordinarily the coils will be assembled close together formaximuminductive relation consistent with practicable clearance between the stationary andmovingcoils. vCoils ,II and I8 are in vertical alignment zabove and below the moving coil in its--zero.--.position and hence are connected to produce .a flux in a vertical direction opposed to torque... Coils i8 and are located in vertical alignment opposite the. up-scale position, of the moving coilend are connected to produce a, flux in the same vertical direction as the-moving coil and hence an attraction torque. Hence as the watt-load-increases the moving coil moves from the zero position shown clockwiseup-scale in accordance with the measurement.

Heretofore the formation of well insulated and ventilated coils of the shape shown and flat spirally wound coils of other shapes generally toby means of bolts passing through openings 22. a

A similar insulating board 23 supports the lower The instrument is shown connected to a line 24 as an alternating current wattmeter. The moving coil II is connected across the line'through spirals I5 and I6 and suitable insulated portions of shaft l0 and the stationary coils are connected in series to a gether with the necessary supporting and terminal structure has been expensive and unsatisfactory. The stationary coils carryvconslderable current and must :be firmly held in place and should have an eflicient cooling arrangement and strong adequate terminal facilities. The formation oi. such coils in accordance with my invention results in very satisfactory coils at low expense. The preferred method of forming such coils will now be described,

In Figs. 1, 2 and 3, 28 represents a metal form having an exterior shape corresponding to the desired internal shape of the coils to be formed and of any convenient length which may be many times the length of the thickness of the individual coils desired. This form has a longitudinal slot 29 for reception of a metal bar 30 which subsequently forms the internal terminals of the finished coils. The bar 30 of rectangular shape corresponding to the shape of slot 29 is brazed or otherwise firmly secured to the end of a metal strip SI which subsequently forms-the windings.

In some cases the bar 30 may be formed by doubling over the end of the strip 3|.

The bar 30 is then seated in the slot 29 of form 28 and the strip 31 wound thereon as illustrated in .Fig. 3. I preferably use a form 28 made from metal since it must have strength to withstand the shocks which it receives during the winding operation-where the strip 3! is of heavy gauge. For example, a hard copper strip 31 of 10 mils thickness needs to be pounded and pressed against the form or the equivalent to bend it substantially-line game -size and ins-"the the ffo'rm i8 "onto! *the spiral collianddrive the .I- tion merely replaces 'the metal form-Mith' -lnsulation.v as mentioned';- previously where aithin contour of the form. Where a thin, easily bent strip is used, I-may usea. formmade out of insulating material.

In winding thestrip 3| on the'form a sheet of insulation '32 such as good'lnsulating-paper, .preierably coated-or impregnated with'an insulating cement, is also wound on between the spiral layers. This .layer tot insulation vseparates and insulates ithe conse'cutive spiral :ti nfns 5offthe gstrip 3i and should 'be started 'before the first complete turn-of strip 3| about the form. Although unnecessary it maybe found convenient-'to sta'rt winding the insulation strlp' with the strlp' fl since then I may insertgthe-innenend oi the-$1 4. 1 :2 in the slot when rtheiba'r "-so ls inserted therein. This will-serve to firmly hold the inner end of the insulation strip the winding on operatlonis started.

The amount of strip '3! and number; ofeturns of the strip which is :thus wound-on-the'form [-18 =is'made "to coniorm tothe' coil size 'and number of turns desired ln the -flnished -coil.- The winding operation -is, o'i' course, accompanied-with sufilcientpressure-rolling;pounding andthe like i to bend the heavy stripfltightly *onto the "dorm I I f andfgive it '-a"ipermanent-'=bend -'to- 'the-- shape of :the -.form.- 'The cement-on or iniithe insulation strip a'ss'ists in #p'reyentingthejspiral of the coil opening up aiter-the-windingpressureis removed.

strip wound on the -iorm sasillus- Thisaoperaeasily beat strip is used toformi the spiralcond'uctor-lay'ers, l-imayfwind it directly upon a form 1 made ofinsulating material-such: as i the: tplug 33,- but where thestrip is :sumciently thick and still. as-to requirejconsiderable pressure. during the winding a'ndforming operation ,as' would likely break or crush a fornimade-of insulating material If then-i1se "the menu form and subsequently' replace ltwith insulation.

- The outer-end of 'theqspirally woundstripmay be bent-and extended in any desired fashion for 50 moldinginsulationaround them. For example,

in making up two coil assemblies such as is shown in the upper and lower stationary coils'of Fig. 1

Iassemble long coils in the desired relative [position in a -moId- 35, F'ig.-5.'-The mold has van .internal shape conforming -to the external .shape of.-the coil assembly desired andthe mold is then illled with a powdered or plastic-insulation 88 "about the cils and pressure-or heataor both are applied, depending upon the type of insulation and molding method *used to set the insulation 70 then 2,334,584 a'r'odnd'the form and make it conform to the insulation is converted into hard form. The

molded insulation may be extended between the coils as shown or the coils may be separated merely by the previously mentioned paper insu- 5 latlon strip.

The structure thus formed is then removed from the mold and has the shape such as shown in Fig. 6. It is a strong, solid-coherent body of rigid construction. v.I then employ a sharp cir- "l0 cular saw and sawgthe blockinto stri s of the desired thickness at right-angles to the conductor therein as for example. along the planes indicated-by dotted lines I'L'Fig. 6. I have found "that a-sharp saw will slice the block into coil 15. assemblies .suchas represented tor-the station- .arylcoilsoffl'fi'g. '1 with a clean'cut and without -leavlng-.prolectlng edges at the cut surfaces of the spiral conductors suchas might otherwise mause-short-cir uts between turns. The thick- 20,; ness of such coil assemblies for an instrument such'as shown in Fig. 1 may be about $4; inch. {In case a dull saw is used "the sawed surfaces should be'subsequently polished to remove any metal between the spiral conductors.- Polishing 25 may also be deslrable for appearance; -In as- Isenibling coils for molding-- find- 81C611 assembly ':'such as; describedi.attention shoiild "be' taken in insertingthe'bdiIs intQ-the moid soas t'ocbtain "the desired direction ofawinding-of' the :coils'. For -example; the right-hand spir'al" as -assembled in isj'-wound-counterclockwise fromcutside to inside. It the q pos'itedirection had been desired the -coilwouldzhave-been =insertedother 'end tou i $5 lt willbenoted trom'il igl lthat the coilsused -=were assembled-slightlydiflerently from that shcwn in Figgfi-and that-to obtain-the different --directions of winding shown-ior-the upper and lowerstationary coil assemblies of Fig. 1- from 40 -the :same block the coil assembly board 23 is merely turned over"-with respect'to board 22.,

=The 'insul'ation designated36 in Figs. b and 6 beccmesthe supporting boardsfi and '23 of Fig. 1'. Supporting bolt-holes and the like such as shown at-22 may be bored-either before-or sub- "sequently to the sawing operation. Likewise, holes may be bored and threaded in thebar 30 which subsequently becomes the internal coll terminals either before ore-subsequently to the sawing operation; It is noted that the terminals are equally accessible from either side of the boards.

- It .is evident that the invention is applicable to the formation .of flat. spirally wound coils of any shape other than the sector shape shown and to the use of such coils or coil assemblies -singly.:on'in multiple with two or more coils assembled into a rigid structure.

The rigid block-like structure such as shown in Fig. 6 may be sold and shipped as an article of commerce and the customergmay saw coils if he wants a coil of a certain current carrying capacity he may sa'w a board from the block, say 4, inch thickand if he wants a-coil of double such current carrying capacity he may saw a board therefrom V inch thick, etc. Holes may be bored in theinner insulation part 33 as shown at 38in Pig. 1 for various purposes. For example to make the structure lighter or for increased ventilation or for the insertion of holding screws or for the insertion of magnetic plugs to modify the flux distribution. Likewise, additional metal inserts or bars may be molded into either the therefrom of the thickness desired. V For example,

inner or outer insulation structure for various purposes.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. The method of producing flat spirally wound electric coils and supporting'structure therefor which consists in tightly rolling up sheets of conductor material and insulating material together such that the internal and external size and shape of the roll conforms to the desired internal and external sire and shape of the coils. providing a tightly fitting core of insulating material within said roll, molding insulating material about said roll to partially imbed the roll therein and thereby forming a solid, rigid, blocklike composite structure and sawing said composite structure into boards running at right angles to the axis of the roll therein and of a thickness conforming to the desired thickness of the coils.

2. The method of producing flat spirally wound electric coils and supporting structure therefor which consists in selecting a metal form of a shape and size conforming to the desired internal size and shape of the coils and of a length considerably longer than the desired thickness of the coils, wrapping a sheet of conductor material and a sheet of insulating material together several times about said form so that the insulating'material lies between adia cent convolutions or the conductor material, forming said conductor material to the shape of the form as the wrapping proceeds, replacing said metal form with an insulator form of the same dimensions, inserting-the roll thus formed in a mold, molding insulating material about the roll to partially imbed the roll therein and forming a solid, rigid-block-like composite structure and then sawing such block-like structure into boards running at right angles to the axis of the conductor roll therein, the boards being of a thickness corresponding to the desired thickness of the coils.

3. The method of forming coil assemblies consisting of a plurality of flat spirally wound coils lying in the same plane in fixed relation to each other which consists in preparing a plurality of rolls each consisting in rolling up a sheet of conductor material with an insulation sheet between the adjacent conductor convolutions of the rolls, providing tightly filling cores of insulating material within said rolls, inserting said rolls in a mold with their axes parallel and in the spaced relation desired, filling the mold about said rolls with insulating material and molding it in place to form a solid composite rigid block in which said rolls arepartially imbedded and firmly held, and sawing said block into boards at right angles to the axis of said rolls, the boards being of a thickness corresponding to the desired thickness of the coil assemblies.

4; The method of forming several similar spirally wound flat electric coils which consists in selecting a metal form of a size and shape conforming to the desired internal size and shape of the coils and of a length several times the thickness of coils desired, forming a terminal slot lengthwise in the external surface of said form, selecting a winding terminal bar and a winding coil sheetoi conductor material and a sheet of insulating material, said bar having alength and said sheets having a lateral dimension corresponding to the length of said form, securing said terminal bar to one edge of said conductor sheet and inserting said bar in the slot of said form to form internal coil terminal structure and anchoring said sheet to said form, wrapping said conductor, sheet and insulation sheet together spirally and several times about said form and shaping the conductor sheet to said form as wrapped, securing the external convolution of said spirally wrapped conductor in place by insulating material molded in place to iorm a solid composite block within which said spirally wound conductor is partially imbedded and then sawing the block into boards running at right angles to the conductor material therein to form flat spirally wound coils of the thickness of such boards.

THEODORE A. RICH.

CERTIFICATE OF coRR cTIoN.' Patent No. 2,551 58h. November 16, 19 45.

. THEODORE A. RICH.

It is hereby certified .that error appears in the printed specification of the above numbered patent requiring correction as follows Psge 1, first column, line 25, for "folded" read --molded---; and that thesaid Letters Patent .should be read with this correction therein that the same may confonn to the record of the case in the Patent Office.

Signed and sealed this 18th day of January, A. 191111..

. Henri Van Arsdale, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION. Patent No. 2,55h,5814.. November 16, 191 .5.

. THEODORE A. HIGH.

It is hereby certifiedthat error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 23, for "folded" read -molded--; and that thesaid Letter; Patent .should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of January, A. D. 19141;.

, -Henry Van Arsdale, (Seal) Acting Commissioner of Pate ts. 

